ChemistryChemistryhttp://hdl.handle.net/2262/332015-03-31T22:02:23Z2015-03-31T22:02:23ZGraphene field emission devicesDUESBERG, GEORG STEFANhttp://hdl.handle.net/2262/732202015-02-17T03:02:19Z2014-01-01T00:00:00ZGraphene field emission devices
DUESBERG, GEORG STEFAN
Graphene field emission devices are fabricated using a scalable process. The field enhancement factors, determined from the Fowler-Nordheim plots, are within few hundreds and match the theoretical predictions. The devices show high emission current density of ∼10 nA μm−1 at modest voltages of tens of volts. The emission is stable with time and repeatable over long term, whereas the noise in the emission current is comparable to that from individual carbon nanotubes emitting under similar conditions. We demonstrate a power law dependence of emission current on pressure which can be utilized for sensing. The excellent characteristics and relative ease of making the devices promise their great potential for sensing and electronic applications
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2014-01-01T00:00:00ZThe application of chiroptical spectroscopy (circular dichroism) in quantifying binding events in lanthanide directed synthesis of chiral luminescent self-assembly structuresGUNNLAUGSSON, THORFINNURhttp://hdl.handle.net/2262/731332015-01-27T03:03:18Z2015-01-01T00:00:00ZThe application of chiroptical spectroscopy (circular dichroism) in quantifying binding events in lanthanide directed synthesis of chiral luminescent self-assembly structures
GUNNLAUGSSON, THORFINNUR
The binding of asymmetrical and optically pure tridentate ligands (L = 1(S) and 1(R)) containing one carboxylic group and 2-naphthyl as an antenna to lanthanide ions (M = La(III) and Eu(III)) was studied in CH3CN, showing the successive formation of M:L, M:L2 and M:L3 stoichiometric species in solution. The europium complexes EuL3 were also synthesised, structurally characterised and their photophysical properties probed in CH3OH and CH3CN. The changes in the chiroptical properties of both 1(S) and 1(R) were used (by circular dichroism (CD) spectroscopy) to monitor the formation of these chiral self-assemblies in solution. While circularly polarised luminescence (CPL) showed the formation of Eu(1(S))3 and Eu(1(R))3 as enantiomers, with high luminescence dissymmetry factors (glum), fitting the CD changes allowed for binding constants to be determined that were comparable to those seen in the analyses of absorbance and luminescence changes.
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2015-01-01T00:00:00ZDisplacement assay detection by a dimeric lanthanide luminescent ternary Tb(iii)-cyclen complex: High selectivity for phosphate and nitrate anionsGUNNLAUGSSON, THORFINNURCAFFREY, DAVIDhttp://hdl.handle.net/2262/731322015-01-27T03:03:16Z2014-01-01T00:00:00ZDisplacement assay detection by a dimeric lanthanide luminescent ternary Tb(iii)-cyclen complex: High selectivity for phosphate and nitrate anions
GUNNLAUGSSON, THORFINNUR; CAFFREY, DAVID
The luminescent dimeric ternary lanthanide–cyclen complexes (2-(Ln.1)2; Ln = Tb/Eu) were designed and both their self-assembly formation and their ability to detect anions via displacement assays were investigated using spectrophotometric titrations in MeOH solution. The formation of 2-(Tb.1)2 and 2-(Eu.1)2 was investigated in solution, and determination of the binding constants and stoichiometry showed that the former was formed almost exclusively over the 1 : 1 complex 2-(Tb.1) after the addition of two equivalents of 2; while for 2-(Eu.1)2 a mixture of both stoichiometries existed even after the addition of four equivalents of 2. Of these two systems, 2-(Tb.1)2 was studied in details as a probe for anions, where significant changes where observed in the photophysical properties of the complex; with the characteristic Tb(III)-centred emission being fully switched off upon the sensing of phosphates and nitrate, giving rise to the formation of a H2PO4−:Tb.1 complex in a 1 : 2 stoichiometry upon sensing of H2PO4− by 2-(Tb.1)2, while NO3− gave 1 : 1 complex formation and two equivalents of NO3−·Tb.1
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2014-01-01T00:00:00ZSynthesis, structural, photophysical and electrochemical studies of various d-metal complexes of btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] ligands that give rise to the formation of metallo-supramolecular gelsGUNNLAUGSSON, THORFINNURBOLAND, JOHNhttp://hdl.handle.net/2262/731312015-01-27T03:03:12Z2014-01-01T00:00:00ZSynthesis, structural, photophysical and electrochemical studies of various d-metal complexes of btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] ligands that give rise to the formation of metallo-supramolecular gels
GUNNLAUGSSON, THORFINNUR; BOLAND, JOHN
2,6-Bis(1,2,3-triazol-4-yl)pyridine (btp) is a terdentate binding motif that is synthesised modularly via the CuAAC reaction. Herein, we present the synthesis of ligands 1 and 2 and the investigation of the coordination chemistry, photophysical behaviour and electrochemistry of complexes of these with a number of d-metal ions (e.g. Ru(II), Ir(III), Ni(II) and Pt(II)). The X-ray crystal structures of ligand 1 and the complexes [Ru·22](PF6)Cl, [Ni·12](PF6)Cl and [Ir·1Cl3] are also presented. All of the complexes displayed non-classical triazolyl C–HCl− hydrogen bonding. All but one complex showed no metal-based luminescence at room temperature, while all of the Pt(II) complexes displayed luminescence at 77 K. The electrochemistry of the Ru(II) complexes was also studied and these complexes were found to have higher oxidation potentials than analogous compounds. The redox behaviour of [RuL2]2+ complexes with both 1 and 2 was nearly identical, while [Ru·1Cl2(DMSO)] was oxidised at significantly lower potential. We also show that the Ru(II) complex of 2, [Ru·22](PF6)Cl, gave rise to the formation of a metallo-supramolecular gel, the morphology of which was studied using scanning electron and helium ion microscopy
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2014-01-01T00:00:00Z